Humic acids: Structural properties and multiple functionalities for novel technological developments

A polyethyleneimine-coated thermally-oxidized graphitic-carbon nitride adsorbent for the removal of organic pollutants

Negatively charged organic pollutants in water are responsible for a large range of public health and ecological issues. Low-cost and low-toxicity graphitic carbon nitride (CN), with its abundant functional groups and surface defects, is a promising material for the removal of organic molecules by adsorption. However, basic synthesis methods for CN often result in a material with morphology and electric charge that are suboptimal for interacting with negatively charged pollutants. Here, an adsorbent was prepared by thermally oxidizing a tubular CN precursor and then coating the resulting flake-shaped material (FCNO) with the polycationic polymer polyethyleneimine (PEI). The resulting adsorbent, FCNO550-PEI, removed humic acid (HA), a widespread problematic organic molecule, as well as the common toxic anionic dye Congo red (CR). FCNO550-PEI was superior to other CN-based adsorbents previously reported in the literature with maximum adsorption capacities according to the Sips isotherm model for HA and CR of 437.1 mg/g and 1430.3 mg/g, respectively. In addition, FCNO550-PEI could adsorb HA and CR from different types of water and was reusable. Besides electrostatic interactions and hydrogen bonds between PEI and the pollutants, HA and CR adsorption was enabled by π-π interactions with the FCNO support itself. The high efficiency of FCNO550-PEI for the removal of HA and CR highlights its potential for water treatment applications.

Humic acid attenuates cisplatin-induced nephrotoxicity in rats

Cisplatin-induced nephrotoxicity, a major limitation of this chemotherapeutic agent, involves oxidative stress, inflammation, and apoptosis. This study investigated the potential renoprotective effects of humic acid in a rat model of cisplatin-induced nephrotoxicity. Forty-two male Wistar rats were assigned to six groups: control, humic acid, cisplatin, cisplatin + humic acid 10 mg/kg, cisplatin + humic acid 20 mg/kg, and cisplatin + humic acid 40 mg/kg. On day 7, the rats were sacrificed, and cardiac blood and kidneys were collected for biochemical and histopathological examinations. Humic acid administration significantly attenuated the cisplatin-induced increases in renal TNF-α and NF-κB levels, indicating a reduction in inflammation. Humic acid also ameliorated histopathological damage, including Bowman's capsule dilatation, tubular cell degeneration, and hemorrhage. However, humic acid did not significantly alter oxidative stress parameters or caspase-3 levels. Humic acid demonstrates a protective effect against cisplatin-induced nephrotoxicity in rats, primarily by mitigating the inflammatory response. While HA's beneficial effects on oxidative stress and apoptosis were limited in this study, its ability to reduce inflammation highlights its potential as a therapeutic strategy to mitigate cisplatin-induced kidney injury.

Humic acid from vermicompost effectively regulates the redox status and mitigates the progression of experimental periodontitis

The progression of periodontal disease (PD) involves the action of oxidative stress mediators. Antioxidant agents may potentially attenuate the development of this condition. Thus, we aimed to evaluate the effects of different doses of humic acid (HA), extracted from biomass vermicomposting, on redox status and parameters related to PD progression in rats. Fifty-four adult male Wistar rats were distributed into six experimental groups (control; PD; PD + 40 mg/kg of HA; PD + 80 mg/kg of HA; PD + 160 mg/kg of HA; PD + 320 mg/kg of HA). HA was administered by gavage for 28 days, and PD was induced by ligature on the mandibular first molars on the 14th day of treatment. After euthanasia, alveolar bone loss, oxidative stress in the gum and erythrocytes, serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and creatinine were analyzed. Animals treated with HA showed less bone loss at the dose of 80 mg/kg compared to the untreated PD group (p < 0.05). Animals treated with HA at doses higher than 80 mg/kg showed improvements in local and systemic redox status parameters (total antioxidant activity, thiobarbituric reactive substances, carbonyl derivatives, and superoxide dismutase) compared to the PD group (p < 0.05). Treatment with HA reduced serum levels of creatinine (at doses of 80 and 160 mg/kg) and AST (at doses of 40 and 80 mg/kg) compared to the PD group (p < 0.05). HA treatment attenuated alveolar bone loss and improved local and systemic oxidative stress parameters in ligature-induced PD rats.

Heat-activated peroxodisulfate oxidation of sulfapyridine: kinetics, transformation pathways, and nitrated byproducts

ABSTRACTThe widespread existence of sulfapyridine (SPD, a typical representative of sulfonamide) in natural environment has raised increasing interest because its potential to cause antibiotic-resistant genes. In this work, the degradation of SPD during heat-activated peroxodisulfate (heat/PDS) oxidation process was explored. The pseudo-first-order rate constant (kobs) of SPD was 0.0149 min-1 with 0.5 mM PDS at pH 7. The kobs values were increased obviously with increasing PDS concentration. Such degradation was ascribed to the oxidation of sulfate radical (SO4•-) primarily according to radical quenching test. A total of 16 transformation products derived from hydroxylation, aniline moiety oxidation, and SO2 extrusion & rearrangement pathways were identified by high-resolution mass spectrometry (HRMS) and theoretical calculations. Of which, the production of nitrated byproducts was attributed to the oxidation of aniline moiety in SPD molecule. The existence of natural organic matter (NOM) obviously reduced the degradation efficiency of SPD, while the effects of coexisting anions (i.e., NO3-, CO32-, and Cl-) were negligible. These findings illustrated that SPD can be effectively degraded but cause the nitrated byproducts generation during the heat/PDS oxidation process, which should be paid attention to when SR-AOPs is applied.

Occurrence of Imipenem in natural water: Effect of dissolved organic matter and metals

The occurrence of trace antibiotic residues in the environment poses a threat by promoting antibiotic resistance and spreading resistant genes. Recent studies show that these residues interact with metals, forming toxic and persistent antibiotic-metal complexes (AMCs). Investigating the photodegradation of these contaminants in environmental waters is essential to understand their fate and ecotoxicological risk assessment in environmental waters. In this sense, the present work delineates the fate of IMP, a carbapenem antibiotic, in the environmental matrix and studies its interactions with humic acid and metals. The study established that the drug was labile and underwent degradation under light and ambient temperatures. Further, analytical studies with dissolved organic matter (DOM), such as humic acids, established an accelerating effect on antibiotic degradation via indirect photochemical pathways. For instance, for a concentration of 100 mg/L IMP mixed with 20 mg/L HA in volumetric ratios of IMP: HA 1:2, 1:1, and 2:1, the final concentrations of IMP after 24 h were 26.11 mg/L (-73.89 %), 34.44 mg/L (-65.56 %), and 44.22 mg/L (55.78 %), respectively. The higher the humic acid, the faster the degradation of IMP, thereby supporting the photochemical generation of reactive oxygen species (OH•) and subsequent oxidative degeneration of the drug. The interactions with metals, specifically copper, accelerated the degradation kinetics of the drug. The promotion effect was owed to the action of the OH• as the oxidizing agent. Based on the degradation products identified by LC-MS/MS, a scheme of the synergistic action of copper-redox coupling and imipenem, resulting in the oxidative degradation of the drug, was proposed. Understanding the photochemical behavior of antibiotics, and their behavior in the presence of DOM and metal is vital for unravelling their fate and complexity in wastewater.

Analysis of Plant Physiological Parameters and Gene Transcriptional Changes Under the Influence of Humic Acid and Humic Acid-Amino Acid Combinations in Maize

The study investigated the application of humic acids (HAs) and a combination of humic acids and amino acids (HA+AA) in maize under field conditions. Based on preliminary data in the literature, the aim was to investigate the effects of the two plant conditioning compounds on plant physiological parameters. In addition to measuring plant physiological parameters in the field, a complete transcriptome analysis was performed to determine exactly which genes were expressed after the treatments and in which physiological processes they play a role. Maize plants showed significant positive yield changes after two priming treatments. Genome-wide transcriptomic analysis revealed the activation of photosynthetic and cellular respiration processes, as well as protein synthesis pathways, which explains the increased yield even under extreme precipitation conditions. The results show that the HA treatment helped in water management and increased the chlorophyll content, while the HA+AA treatment led to higher protein and dry matter contents. The post-harvest tests also show that the HA+AA treatment resulted in the highest yield parameters. Functional annotation of the maize super transcriptome revealed genes related to translation processes, photosynthesis, and cellular respiration. The combined pathway analysis showed that the HA and combined treatments activated genes related to photosynthesis, carbon fixation, and cellular respiration, providing valuable in-depth insight into the usefulness of the HA and HA+AA treatments in priming. Based on the studies, we believe that the use of natural-based humic acid plant conditioners may provide a beneficial opportunity to promote renewable, regenerative agriculture.

Analysis of interactions between pharmaceuticals and humic acid: Characterization using entrapment and high-performance affinity microcolumns

The presence of pharmaceuticals as microcontaminants in the environment has become of particular concern given the growing increase in water reuse and recycling to promote global sustainability of this resource. Pharmaceuticals can often undergo reversible interactions with soluble dissolved organic material such as humic acid, which may be an important factor in determining the bioavailability and effects of these compounds in the environment. In this study, high-performance affinity microcolumns containing non-covalently entrapped and immobilized humic acid are used to examine the binding strength and interactions of this agent for tetracycline, carbamazepine, ciprofloxacin, and norfloxacin, all common pharmaceutical microcontaminants known to bind humic acid. The binding constants, as measured with Aldrich humic acid, have good agreement with values reported in the literature. In addition, the effects of temperature, ionic strength, and pH on these interactions are examined with the humic acid microcolumns. This technique makes it possible to determine the relative importance of electrostatic interactions vs non-polar interactions or hydrogen bonding on these binding processes. This study illustrates how affinity microcolumns can be used to screen and uniformly quantify binding by pharmaceuticals with humic acid, as well as to study the mechanisms of these interactions, with this information often being acquired in minutes and with small amounts of binding agent (∼10 mg per microcolumn, which could be used over 200-300 experiments). Use of entrapment and affinity microcolumns can support similar research for a wide range of other microcontaminants with humic acid or alternative binding agents found in water and the environment.

Influence of Organic Matter and Speciation on the Dynamics of Trace Metal Adsorption on Microplastics in Marine Conditions

Dissolved organic matter (DOM), primarily in the form of humic acid (HA), plays a crucial role in trace metal (TM) speciation and their subsequent adsorption dynamics on microplastics (MP) in aquatic environments. This study evaluates the impact of environmentally relevant concentrations of HA on the adsorption behaviors of essential (Co, Cu, Ni, and Zn) and toxic (Cd and Pb) TMs onto polyethylene (PE) and polypropylene (PP) pellets, as well as PP fibers under marine conditions, during a six-week experiment. The HA concentrations were 0.1, 1, and 5 mg/L, while all metals were in the same amounts (10 µg/L). Results reveal that HA significantly influences the adsorption of Cu, Pb, and Zn on MP, particularly on PP fibers, which exhibited the greatest TM adsorption dynamics. The adsorption patterns correspond to the concentrations of these metals in seawater, with the sequence for pellets being Zn > Cu > Pb > Ni > Co~Cd, and for fibers Cu > Zn > Pb > Co~Ni > Cd. Speciation modeling supported these findings, indicating that Cu, Pb, and Zn predominantly associate with HA in seawater, facilitating their adsorption on MP, whereas Cd, Co, and Ni mainly form free ions and inorganic complexes, resulting in slower adsorption dynamics. Statistical analysis confirmed the influence of HA on the adsorption of Cd, Pb, Cu, and Ni. By investigating the dynamics of TM adsorption on plastics, the influence of DOM on these two contaminants under marine conditions was evaluated. The presented results can help in forming a better understanding of synergistic plastic and trace metal pollution in marine systems that are relevant at the global level, since both contaminants pose a serious threat to aquatic ecosystems.

Reclaiming selenium from water using aluminum-modified biochar: Adsorption behaviors, mechanisms, and effects on growth of wheat seedlings

Although selenium is an essential nutrient, its contamination in water poses serious risks to human health and ecosystems. In this study, aluminum-modified bamboo biochar (Al-BC) was developed to reclaim Se(VI) from water. Compared to pristine biochar (BC), Al-BC had a larger specific surface area (176 m2/g) and pore volume (0.180 cm³/g). The modification, achieved by loading AlOOH and Al2O3 particles onto the surface, enabled Al-BC to achieve a maximum adsorption capacity of 37.6 mg/g for Se(VI) within 2 h and remove 99.6% of Se(VI) across a pH range of 3-10. The main adsorption mechanism of Se(VI) involved electrostatic attraction, forming outer-sphere complexes between Se(VI) and AlOOH sites on the biochar. The bioavailability of Se sorbed on the spent biochar (Al-BC-Se) was thus evaluated. It was discovered that Al-BC-Se successfully released Se(VI), which impacted the growth of wheat seedlings. The Se content reached 134 μg/g dry weight (DW) in wheat shoots and 638 μg/g DW in roots, significantly exceeding normal selenium content (<40 μg/g DW). By successfully applying the modified biochar to capture selenium from water through adsorption and then reusing it as an essential nutrient in soil, this study suggests the promising feasibility of the "removal-collection-reuse" approach for the circular economy of selenium in wastewater.

A strategy for quantifying microplastic particles in membrane filtration processes using flow cytometry

Microplastic (MP) pollution is ubiquitous in the aquatic environment, with significant quantities of MPs originating from municipal wastewater treatment plants. Efforts to evaluate and implement MP removal processes are underway, with membrane technologies often recommended as an "ideal" solution. A key challenge in evaluating these technologies involves efficiently quantifying MP concentrations in samples. Here, flow cytometry (FC) is demonstrated as an effective technique to obtain concentration measurements of plastic microbeads (MBs; 1-5 μm) suspended in water with/without added humic acid. Regardless of solution conditions, MB concentrations were easily quantified via FC. Subsequently, two microfiltration membranes were challenged to these suspensions. As measured via FC, the 0.45 μm membrane demonstrated effective MB rejection (>99%) whereas the 5 μm membrane exhibited a broad range of rejections (40% to >95%) depending on solution conditions and filtration time. Finally, a model was formulated utilizing FC forward light scattering intensity measurements to estimate MB sizes in samples. Using the model, a 33% reduction in median MB size, on average, was noted across the 5 μm membrane when filtering MBs suspended in humic acid solution, affirming a preferential permeation of smaller particles. Overall, this study advances MP quantification techniques towards validating removal processes.

Participation of strong charge-assisted hydrogen bonds in interactions of dissolved organic matter represented by Suwannee River Humic Acid

Terrestrial dissolved organic matter (DOM) plays critical roles in many biotic and abiotic environmental reactions as well as in water treatment. Its structure is therefore of great interest. We examined dissolved Suwannee River Humic Acid (HA) to probe the potential participation of exceptionally strong, negative charge-assisted hydrogen bonds, (-)CAHB, in DOM cohesion and interaction with small weak acids using high performance size exclusion chromatography (HPSEC), transmission electron microscopy, zeta-pH curves, and pH drift experiments. The results support a previously proposed two-tier state of aggregation, in which tightly-knit primary particles (≤ ∼10 kDa) form larger secondary aggregates (up to micrometer in size). Evidence for (-)CAHB is gained through zeta potential changes and pH drift experiments. The primary particles interact with (-)CAHB-capable solutes (simple carboxylic acids and phosphate) but not (-)CAHB-incapable solutes. We identified disruption of intra-segmental and inter-molecular (-)CAHB leading to swelling and disaggregation, as well as formation of nouveau (-)CAHB with free groups on HA. The effects were solute-concentration dependent and greater at pH 5 than pH 6, consistent with CAHB theory. Phosphate induced the greatest shifts in the HPSEC molecular size distribution curves. The shifts were unaffected by prior stripping of innate polyvalent metals. We conclude that the (-)CAHB contributes to the cohesion of DOM, affecting its size and charge, and provides a means by which weak acid pollutants, nutrients, and natural compounds can interact with DOM. Such interactions have implications for the behavior of DOM in the environment, the fate and transport of anthropogenic pollutants, and the roles DOM play in water treatment technologies.

Geobatteries in environmental biogeochemistry: Electron transfer and utilization

The efficiency of direct electron flow from electron donors to electron acceptors in redox reactions is significantly influenced by the spatial separation of these components. Geobatteries, a class of redox-active substances naturally present in soil-water systems, act as electron reservoirs, reversibly donating, storing, and accepting electrons. This capability allows the temporal and spatial decoupling of redox half-reactions, providing a flexible electron transfer mechanism. In this review, we systematically examine the critical role of geobatteries in influencing electron transfer and utilization in environmental biogeochemical processes. Typical redox-active centers within geobatteries, such as quinone-like moieties, nitrogen- and sulfur-containing groups, and variable-valent metals, possess the potential to repeatedly charge and discharge. Various characterization techniques, ranging from qualitative methods like elemental analysis, imaging, and spectroscopy, to quantitative techniques such as chemical, spectroscopic, and electrochemical methods, have been developed to evaluate this reversible electron transfer capacity. Additionally, current research on the ecological and environmental significance of geobatteries extends beyond natural soil-water systems (e.g., soil carbon cycle) to engineered systems such as water treatment (e.g., nitrogen removal) and waste management (e.g., anaerobic digestion). Despite these advancements, challenges such as the complexity of environmental systems, difficulties in accurately quantifying electron exchange capacity, and scaling-up issues must be addressed to fully unlock their potential. This review underscores both the promise and challenges associated with geobatteries in responding to environmental issues, such as climate change and pollutant transformation.

Nanoarchitecture-Integrated Hydrogel Boosts Angiogenesis-Osteogenesis-Neurogenesis Tripling for Infected Bone Fracture Healing

Infected fracture healing is a complicated process that includes intricate interactions at the cellular and molecular levels. In addition to angiogenesis and osteogenesis, the significance of neurogenesis in fracture healing has also been recognized in recent years. Here, a nanocomposite hydrogel containing pH-responsive zinc-gallium-humic acids (HAs) nanoparticles is developed. Through the timed release of Zn2+, Ga3+, and HAs, the hydrogel exhibits potent antibacterial effects and promotes angiogenesis, osteogenesis, and neurogenesis. The enhanced neurogenesis further promotes angiogenesis and osteogenesis, forming a mutually supportive angiogenesis-osteogenesis-neurogenesis cycle at the fracture site. The hydrogel achieves rapid infected fracture healing and improves tissue regeneration in mice. This study proposes a comprehensive treatment approach that combines antibacterial effects with the regulation of tissue regeneration to improve infected fracture healing.

Effect of amikacin-humic acid combination on Acinetobacter baumannii biofilm: an in vitro and in silico study

Aim: Acinetobacter baumannii (AB) is a clinically important bacterial pathogen responsible for nosocomial infections. The biofilm-forming capability of these pathogens reduces the antibiotic penetration and its efficacy, thereby complicating the treatment. The current work aims to isolate the most potent biofilm-forming Acinetobacter species from clinical isolates of the patient samples and to evaluate the efficacy of the amikacin-humic acid combination against it.Methods: The combination effect of Amikacin-Humic (AMK-HUM) acid against the highest biofilm-producing A. baumannii SLMK001 was studied via in-vitro (microscopic analysis) and in-silico (Network Pharmacology) analysis.Results: The amikacin-humic acid combination significantly inhibited both the biofilm formation and cell viability of A. baumannii SLMK001. The images observed via Scanning Electron Microscope (SEM) showed a significant decrease in the biofilm matrix. Confocal Laser Scanning Microscope (CLSM) confirmed a reduction of the Z value of its three-dimensional structure. Further, the Network Pharmacology approach supported these experimental findings by identifying the key targets of the amikacin-humic acid combination against the biofilm pathways of A. baumannii.Conclusion: The in-vitro results aligned with the in-silico findings, indicating that the AMK-HUM combination is a promising treatment that significantly activates the key proteins against A. baumannii biofilm formation and pathogenesis.

Process Condition Optimization and Structural Feature Analysis of Humic Acid Extraction from Weathered Lignite

In this study, response surface methodology (RSM) was adopted to investigate the optimization of process conditions for extracting humic acid (HA) from coal, aiming to enhance the yield of humic acid. Additionally, UV-vis spectroscopy, FTIR, XRD, TG-DTG, CP/MAS13CNMR, XPS, and molecular fluorescence were utilized to examine the properties of HAs. The extraction time significantly influenced the yield from Lishi weathered lignite, while the liquid-solid ratio had a significant impact on the yield from Wuhai weathered lignite. The interactive effect between factors did not have a significant effect on the yield. The optimal extraction conditions for Lishi humic acid (LSHA) were determined to be an extraction time of 4.4 h, NaOH concentration of 0.30 mol/L, and liquid-solid ratio of 21 mL/g, while those for Wuhai humic acid (WHHA) were 3.1 h, 0.21 mol/L, and 12 mL/g, respectively. Under these optimal conditions, the true yield values closely matched the predicted value obtained from the model optimization. Comparative analysis of the HAs revealed similarities in their chemical properties, including the degree of aromaticity, molecular weight, and distribution of functional groups. The aromaticity of WHHA was higher compared to that of LSHA. The higher hydrophilic-hydrophobic index of LSHA contributed to its relatively high biological activity compared to that of WHHA. Both humic acids belong to terrestrial humic acids. The results of the study provide a reference for further application of humic acid.

Insights into the characteristics of changes in dissolved organic matter fluorescence components on the natural attenuation process of toluene

Natural attenuation (NA) is of great significance for the remediation of contaminated groundwater, and how to identify NA patterns of toluene in aquifers more quickly and effectively poses an urgent challenge. In this study, the NA of toluene in two typical soils was conducted by means of soil column experiment. Based on column experiments, dissolved organic matter (DOM) was rapidly identified using fluorescence spectroscopy, and the relationship between DOM and the NA of toluene was established through structural equation modeling analysis. The adsorption rates of toluene in clay and sandy soil were 39 % and 26 %, respectively. The adsorption capacity and total NA capacity of silty clay were large. The occurrence of fluorescence peaks of protein-like components and specific products indicated the occurrence of biodegradation. Arenimonas, Acidovorax and Brevundimonas were the main degrading bacteria identified in Column A, while Pseudomonas, Azotobacter and Mycobacterium were the main ones identified in Column B. The pH, ORP, and Fe(II) were the most important factors affecting the composition of microbial communities, which in turn affected the NA of toluene. These results provide a new way to quickly identify NA of toluene.

Biodegradation of humic acids by Streptomyces rochei to promote the growth and yield of corn

Humic acids (HAs) are organic macromolecules that play an important role in improving soil properties, plant growth and agronomic parameters. However, the feature of relatively complex aromatic structure makes it difficult to be degraded, which restricts the promotion to the crop growth. Thus, exploring microorganisms capable of degrading HAs may be a potential solution. Here, a HAs-degrading strain, Streptomyces rochei L1, and its potential for biodegradation was studied by genomics, transcriptomics, and targeted metabolomics analytical approaches. The results showed that the high molecular weight HAs were cleaved to low molecular aliphatic and aromatic compounds and their derivatives. This cleavage may be associated with the laccase (KatE). In addition, the polysaccharide deacetylase (PdgA) catalyzes the removal of acetyl groups from specific sites on the HAs molecule, resulting in structural changes. The field experiment showed that the degraded HAs significantly promote the growth of corn seedlings and increase the corn yield by 3.6 %. The HAs-degrading products, including aromatic and low molecular weight aliphatic substances as well as secondary metabolites from S. rochei L1, might be the key components responsible for the corn promotion. Our findings will advance the application of HAs as soil nutrients for the green and sustainable agriculture.

Perspectives for Photocatalytic Decomposition of Environmental Pollutants on Photoactive Particles of Soil Minerals

The literature shows that both in laboratory and in industrial conditions, the photocatalytic oxidation method copes quite well with degradation of most environmental toxins and pathogenic microorganisms. However, the effective utilization of photocatalytic processes for environmental decontamination and disinfection requires significant technological advancement in both the area of semiconductor material synthesis and its application. Here, we focused on the presence and "photocatalytic capability" of photocatalysts among soil minerals and their potential contributions to the environmental decontamination in vitro and in vivo. Reactions caused by sunlight on the soil surface are involved in its normal redox activity, taking part also in the soil decontamination. However, their importance for decontamination in vivo cannot be overstated, due to the diversity of soils on the Earth, which is caused by the environmental conditions, such as climate, parent material, relief, vegetation, etc. The sunlight-induced reactions are just a part of complicated soil chemistry processes dependent on a plethora of environmental determinates. The multiplicity of affecting factors, which we tried to sketch from the perspective of chemists and environmental scientists, makes us rather skeptical about the effectiveness of the photocatalytic decontamination in vivo. On the other hand, there is a huge potential of the soils as the alternative and probably cheaper source of useful photocatalytic materials of unique properties. In our opinion, establishing collaboration between experts from different disciplines is the most crucial opportunity, as well as a challenge, for the advancement of photocatalysis.

Complexation with Metal Ions Affects Chlorination Reactivity of Dissolved Organic Matter: Structural Reactomics of Emerging Disinfection Byproducts

Metal ions are liable to form metal-dissolved organic matter [dissolved organic matter (DOM)] complexes, changing the chemistry and chlorine reactivity of DOM. Herein, the impacts of iron and zinc ions (Fe3+ and Zn2+) on the formation of unknown chlorinated disinfection byproducts (Cl-DBPs) were investigated in a chlorination system. Fe3+ preferentially complexed with hydroxyl and carboxyl functional groups, while Zn2+ favored the amine functional groups in DOM. As a consequence, electron-rich reaction centers were created by the C-O-metal bonding bridge, which facilitated the electrophilic attack of α-C in metal-DOM complexes. Size-reactivity continuum networks were constructed in the chlorination system, revealing that highly aromatic small molecules were generated during the oxidation and decarbonization of metal-DOM complexes. Molecular transformation related to C-R (R represents complex sites) loss was promoted via metal complexation, including decarboxylation and deamination. Consequently, complexation with Fe3+ and Zn2+ promoted hydroxylation by the C-O-metal bonding bridge, thereby increasing the abundances of unknown polychlorinated Cl-DBPs by 9.6 and 14.2%, respectively. The study provides new insights into the regulation of DOM chemistry and chlorine reactivity by metal ions in chlorination systems, emphasizing that metals increase the potential health risks of drinking water and more scientific control standards for metals are needed.

Biodegradable Cassava Starch/Phosphorite/Citric Acid Based Hydrogel for Slow Release of Phosphorus: In Vitro Study

Phosphorous (P) is one the most important elements in several biological cycles, and is a fundamental component of soil, plants and living organisms. P has a low mobility and is quickly adsorbed on clayey soils, limiting its availability and absorption by plants. Here, biodegradable hydrogels based on Cassava starch crosslinked with citric acid (CA) were made and loaded with KH2PO4 and phosphorite to promote the slow release of phosphorus, the storing of water, and the reduction in P requirements during fertilization operations. Crosslinking as a function of CA concentrations was investigated by ATR-FTIR and TGA. The water absorption capacity (WAC) and P release, under different humic acid concentration regimens, were studied by in vitro tests. It is concluded that hydrogel formed from 10% w/w of CA showed the lowest WAC because of a high crosslinking degree. Hydrogel containing 10% w/w of phosphorite was shown to be useful to encouraging the slow release of P, its release behavior being fitted to the Higuchi kinetics model. In addition, P release increased as humic acid contents were increased. These findings suggest that these hydrogels could be used for encouraging P slow release during crop production.

Combined effects of pH and dissolved organic matter on the availability of pharmaceuticals and personal care products in aqueous environment

The interaction between pharmaceuticals and personal care products (PPCPs) with dissolved organic matter (DOM) can alter their bioavailability and toxicity. Nevertheless, little is known about how pH and DOM work together to affect the availability of PPCPs. This study investigated the impact of pH and DOM on the availability of seven PPCPs, namely Carbamazepine, Estrone, Bisphenol A, Testosterone Propionate, Triclocarban, 4-tert-Octylphenol and 4-n-Nonylphenol, using negligible depletion solid-phase microextraction (nd-SPME). The uptake kinetics of PPCPs by the nd-SPME fibers increased proportionally with DOM concentrations, likely due to enhanced diffusive conductivity in the unstirred water layer. At neutral pH, the partitioning coefficients of PPCPs for Humic Acid (log KDOC 3.87-5.25) were marginally higher than those for Fulvic Acid (log KDOC 3.64-5.11). Also, the log KDOC values correlated linearly with the log DOW (pH 7.0) values of PPCPs, indicating a predominant role for hydrophobic interactions in the binding of DOM and PPCPs. Additionally, specific interactions like hydrogen bonding, π-π, and electrostatic interactions occur for certain compounds, influenced by the polarity and spatial conformation of the compounds. For these ionizable PPCPs, the log DDOC values exhibit a strong dependence on pH due to the dual influence of pH on both DOM and PPCPs. The log DDOC values rose from pH 1.0 to 3.0, peaked at pH 5.0 to 9.0, and then (sharply) declined from 11.0 to 13.0. The reasons are that in strong acidic circumstances, the coiled and compressed shape of DOM inhibits the hydrophobic interaction, whereas in strong alkaline conditions, significant electrostatic repulsion reduces the sorption. This study reveals that the effects of DOM on the bioavailability of PPCPs are dependent on both pH and the specific compound involved.

Selective Modifier-Assisted Humic Acid Extraction: Implications for Soil Quality Enhancement

Efficient use of humic acid (HA) for eco-friendly farming and environmental remediation requires further understanding of how targeted modification of HA affects the chemical structure of HA and thereby its effectiveness in enhancing soil quality. We developed novel selective modifiers (SMs) for extracting HA by codoping sodium and copper elements into the birnessite lattice. The structure of SMs was thoroughly examined, and the HAs extracted using SMs, referred to as SMHs, were subjected to a detailed evaluation of their functional groups, molecular weight, carbon composition, flocculation limits, and effectiveness in saline soil remediation. The results showed that replacing manganese with sodium and copper in SMs alters the valence state and reactive oxygen species. In contrast, SMHs exhibited increased acidic functional groups, a lower molecular weight, and transformed aliphatic carbon. Furthermore, the saline soil was improved through increased salt leaching and an optimized soil aggregate structure by SMHs. This research highlights the importance of targeted modification of HA and demonstrates the potential of these modifiers in improving soil quality for eco-friendly farming and environmental remediation.

Ultrasound-Assisted Synthesis of Humic-Silica Composites by the Isolation of Humic Substances from Peat and Lignite

The aim of the presented study was to evaluate an integrated, direct procedure for the synthesis of humic-silica composites (HSiC) by the isolation of humic substances (HS) from peat and lignite by the use of sodium silicate solution as an extractant. The obtained materials, because of the presence of humic functional groups, may potentially be used for removing contaminants from aqueous solutions. The quantitative assessment was based on experiments designed according to the Box-Behnken plan. The statistical analysis of the results allowed to determine the optimal conditions of the process tested, for which the isolation efficiency of humic substances (HS) was greater than 50 % for both raw materials. This made it possible to synthesize humic silica composites with a high content of HS, which have been qualitatively evaluated. This step was focused on the analysis of the humic structure using elemental analysis, spectroscopic methods, and differential thermal analysis coupled with thermogravimetry. On the basis of them, the presence of structures characteristic for HS in the HSiC tested was observed. Moreover, the results of the thermal analysis pointed to the higher thermal stability of the synthesized compounds, compared to the HS isolated with the use of a traditional extractant.

Spraying humic acid regulator on cultivated Codonopsis pilosula (Franch.) Nannf. to improve yield of active constituents

Plant growth regulators have been used in the cultivation of medicinal plants to increase yield, but the existing regulators decreased the content of active constituents which benefit human health. Therefore, it is necessary to find a new growth regulator to achieve the win-win goal of increasing yield and improving active constituents' accumulation. The potential of replacing chlorocholine chloride with a new humic acid-based growth regulator was evaluated by measuring the yield and active constituents' accumulation of Codonopsis pilosula. Three treatments including water (CK), chlorocholine chloride (T1) and humic acid regulator (T2) were applied by foliar spraying. Among them, both chlorocholine chloride and humic acid regulator belong to biostimulant. The result showed that the root yield in T1 and T2 were significantly increased by 59.1% and 54.9% compared with CK, respectively, and there was no significant difference between T1 and T2. Compared with CK, the yields of lobetyolin, syringin and atractylenolide III of Codonopsis pilosula were significantly decreased by 6.3%, 7.3% and 13.0% in T1, but were significantly increased by 22.8%, 14.8% and 32.0% in T2, respectively. Redundancy analyses showed that photosynthetic rate, sucrose phosphoric acid synthetase and phosphomannomutase had higher degree of explanation for yield and quality. Linear regression results indicated that photosynthetic rate and phosphomannomutase were the main factors to affect yield and active constituents yields, respectively. In addition, the output-input ratios based on the yields of polysaccharides, lobetyolin, syringin and atractylenolide III of Codonopsis pilosula in T2 was significantly increased by 6.5%, 15.2%, 8.7% and 31.2% respectively as compared with T1. Overall, compared with water treatment, both chlorocholine chloride and humic acid regulator treatments can increase the root yield of Codonopsis pilosula. Compared with chlorocholine chloride, humic acid regulator can improve the yield of active constituents and economic benefits of Codonopsis pilosula. This study indicated that reasonable selection of plant growth regulators is of great significance for achieving a win-win goal of increasing the root yield and active constituents of medicinal plants.

Characterizing Macroporous Ion Exchange Membrane Adsorbers for Natural Organic Matter (NOM) Removal-Adsorption and Regeneration Behavior

Addressing the characterization of Natural Organic Matter (NOM) removal by functionalized membranes in water treatment, this study evaluates the effectiveness of two commercial ion-exchange membrane adsorbers: Sartobind® Q (with quaternary amines) and D (with tertiary amines). Using Suwannee River NOM (SRNOM) as a surrogate, Langmuir adsorption isotherms revealed maximum capacities (Qmax) of 2966 ± 153 mg C/m2 and 2888 ± 112 mg C/m2, respectively. Variations in flux from 50 to 500 LMH had a minimal impact on breakthrough times, proving low diffusion limitations. The macroporous (3-5 µm) functionalized cellulose-based membranes exhibited high permeabilities of 10,800 L/(h m2 bar). Q maintained positive zeta potential vs. pH, while D's zeta potential decreased above pH 7 due to amine deprotonation and turning negative above an isoelectric point of 9.1. Regeneration with 0.01 M NaOH achieved over 95% DOC regeneration for Sartobind® D, characterizing reversibility through a pH-swing. Cyclic adsorption showed that Q maintained its capacity with over 99% DOC regeneration, while D required acidic conditioning after the first regeneration cycle to mitigate capacity reduction and re-deprotonate the adsorber. These results have demonstrated the potential suitability of adsorber membranes, designed originally for biotechnological purposes, for the possible removal of disinfection byproduct precursors in drinking water treatment.

Facile preparation of environmental benign LED white light active humic acid nanolayer coated titanium dioxide photocatalyst for bisphenol A degradation

Natural organic matter is a mixture of microbial decomposition products widely found in surface and groundwater. These organic materials have great potential as carbon-based precursors for chemical synthesis. This work demonstrated the development of a green photocatalyst via a facile adsorption process that combined colloidal titanium dioxide (TiO2) with humic acid. The resulting photocatalyst was visible light active and able to completely degrade 5 mg/L of BPA within 6 h under the irradiation of energy-efficient LED white light. The first-order kinetic rate constant of the reaction was determined to be 1.7 × 10-2 min-1. The enhanced photocatalytic activity was attributed to the decreased band gap energy and effective charge separation that limits the photogenerated electron-hole recombination. The outcome of this research opened an opportunity for the development of sustainable functional materials using natural organic matter.

Protective effects of sodium humate and its zinc and selenium chelate on the oxidative stress, inflammatory, and intestinal barrier damage of Salmonella Typhimurium-challenged broiler chickens

The objective of this study was to investigate the protective effects and mechanisms of dietary administration of sodium humate (HNa) and its zinc and selenium chelate (Zn/Se-HNa) in mitigating Salmonella Typhimurium (S. Typhi) induced intestinal injury in broiler chickens. Following the gavage of 109 CFU S. Typhi to 240 broilers from 21-d to 23-d aged, various growth performance parameters such as body weight (BW), average daily gain (ADG), average daily feed intake (ADFI), and feed ratio (FCR) were measured before and after infection. Intestinal morphology was assessed to determine the villus height, crypt depth, and chorionic cryptologic ratio. To evaluate intestinal barrier integrity, levels of serum diamine oxidase (DAO), D-lactic acid, tight junction proteins, and the related genes were measured in each group of broilers. An analysis was conducted on inflammatory-related cytokines, oxidase activity, and Nuclear Factor Kappa B (NF-κB) and Nuclear factor erythroid2-related factor 2 (Nrf2) pathway-related proteins and mRNA expression. The results revealed a significant decrease in BW, ADG, and FCR in S. typhi-infected broilers. HNa tended to increase FCR (P = 0.056) while the supplementation of Zn/Se-HNa significantly restored BW and ADG (P < 0.05). HNa and Zn/Se-HNa exhibit favorable and comparable effects in enhancing the levels of serum DAO, D-lactate, and mRNA and protein expression of jejunum and ileal tight junction. In comparison to HNa, Zn/Se-HNa demonstrates a greater reduction in S. Typhi shedding in feces, as well as superior efficacy in enhancing the intestinal morphology, increasing serum catalase (CAT) activity, inhibiting pro-inflammatory cytokines, and suppressing the activation of the NF-κB pathway. Collectively, Zn/Se-HNa was a more effective treatment than HNa to alleviate adverse impact of S. Typhi infection in broiler chickens.

Super capacity of ligand-engineered biochar for sorption of malachite green dye: key role of functional moieties and mesoporous structure

This study synthesized a new thiomalic acid-modified rice husk biochar (TMA-BC) as a versatile and eco-friendly sorbent. After undergoing chemical treatments, the mercerized rice husk biochar (NaOH-BC) and TMA-BC samples showed higher BET surface area values of 277.1 m2/g and 305.8 m2/g, respectively, compared to the pristine biochar (BC) sample, which had a surface area of 234.2 m2/g. In batch adsorption experiments, it was found that the highest removal efficiency for malachite green (MG) was achieved with TMA-BC, reaching 96.4%, while NaOH-BC and BC exhibited removal efficiencies of 38.6% and 27.9%, respectively, at pH 8. The engineered TMA-BC exhibited a super adsorption capacity of 104.17 mg/g for MG dye at pH 8.0 and 25 °C with a dosage of 2 g/L. The SEM, TEM, XPS, and FTIR spectroscopy analyses were performed to examine mesoporous features and successful TMA-BC carboxylic and thiol functional groups grafting on biochar. Electrostatic forces, such as π - π interactions, hydrogen bonding, and pore intrusion, were identified as key factors in the sorption of MG dye. As compared to single-solution adsorption experiments, the binary solution experiments performed at optimized dosages of undesired ions, such as humic acid, sodium dodecyl sulfate surfactant, NaCl, and NaSCN, reflected an increase in MG dye removal of 2.8%, 8.7%, 5.4%, and 12.7%, respectively, which was attributed to unique mesoporous features and grafted functional groups of TMA-BC. Furthermore, the TMA-BC showed promising reusability up to three cycles. Our study indicates that mediocre biochar modified with TMA can provide an eco-friendly and cost-effective alternative to commercially accessible adsorbents.

Using CuMgFe layered double oxide to replace laccase as a catalyst for abiotic humification

Humification offers a promising avenue for sequestering dissolved organic carbon while facilitating environmental cleanup. In this study, CuMgFe layered double oxides (LDO) were applied as a catalyst to replace conventional enzymes, such as laccase, thereby enhancing the in vitro polyphenol-Maillard humification reaction. CuMgFe LDO was synthesized through calcination of CuMgFe layered double hydroxides (LDH) at 500 °C for 5 h. A suite of characterization methods confirmed the successful formation into mixed oxides (Cu2O, CuO, MgO, FeO, and Fe2O3) after thermal treatment. A rapid humification reaction was observed with CuMgFe LDO, occurring within a two-week span, likely due to a distinct synergy between copper and iron elements. Subsequent analyses identified that MgO in CuMgFe LDO also played a pivotal role in humification by stabilizing the pH of the reaction. In the absence of magnesium, LDO's humification activity was more pronounced in the early stages of the reaction, but it rapidly diminished as the reaction progressed. The efficiency of CuMgFe LDO was heightened at elevated temperatures (35 °C), while light conditions manifested a discernible effect, with a modest decrease in humification efficacy under indoor light exposure. CuMgFe LDO surpassed both laccase and MgFe LDH in performance, boasting a superior humification efficiency relative to its precursor, CuMgFe LDH. The catalysts' humification activity was modulated by their crystallinity and valence dynamics. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) results suggested that introducing the amino acid, glycine, expedited the CuMgFe LDO-fueled humification, enhancing the formation of C-N and C-C bonds in the resultant products. The humic-like substances derived from the catalyst-enhanced reaction displayed an elevated presence of aromatic configurations and a richer array of oxygen functional groups in comparison to a typical commercial humic material.

Organic cocatalysts improved Fenton and Fenton-like processes for water pollution control: A review

In recent times, organic compounds have been extensively utilized to mitigate the limitations associated with Fe(Ⅲ) reduction and the narrow pH range in Fenton and Fenton-like processes, which have garnered considerable attention in relevant studies. This review presents the latest advancements in the comprehensive analysis and applications of organic agents as assistant/cocatalysts during Fenton/Fenton-like reactions for water pollution control. The primary focus includes the following: Firstly, the mechanism of organic co-catalytic reactions is introduced, encompassing both complexation and reduction aspects. Secondly, these organic compounds are classified into distinct categories based on their functional group structures and applications, namely polycarboxylates, aminopolycarboxylic acids, quinones, phenolic acids, humic substances, and sulfhydryl compounds, and their co-catalytic functions and mechanisms of each category are discussed in meticulous detail. Thirdly, a comprehensive comparison is conducted among various types of organic cocatalysts, considering their relative merits, cost implications, toxicity, and other pertinent factors. Finally, the review concludes by addressing the universal challenges and development prospects associated with organic co-catalytic systems. The overarching objective of this review is to provide insights into potential avenues for the future advancement of organic co-catalytic Fenton/Fenton-like reactions in the context of water purification.

Unlocking the Therapeutic Potential of Freshwater Sapropel Extracts: In Vitro Analysis and Antioxidant Profiling for Skincare Applications

Background and Objective: Sapropel, a biologically active sedimentary deposit, is high in organic matter and minerals and has been shown to offer health benefits. Its constituents, humic acid (HA) and fulvic acid (FA), have been found to have some therapeutic applications. The aim of this study was to determine the potential therapeutically significant properties of freshwater sapropel extracts: their polyacid content, antioxidative (AO) status, and biological activity in cell culture. Materials and Methods: Freshwater lakes from the southeast region of Latvia were investigated layer by layer. The total organic carbon (TOC) was determined through combustion using the catalytic oxidation method, HA and FA were measured via acid perspiration, and the total polyphenol content (TPC) and total antioxidant status (TAS) was analysed spectrophotometrically. Sapropel extracts' regenerative abilities were tested in vitro using a Cell-IQ real-time monitoring system on mouse BALB/c 3T3 fibroblasts and human keratinocyte HaCaT cell lines. Cytotoxicity was measured through neutral red uptake assessment as a concentration-dependent reduction in the uptake of neutral red dye relative to a vehicle control or untreated cells. Results: The highest AO activity was observed in sapropel extracts with elevated concentrations of HA and TPC from Audzelu Lake (1.08 ± 0.03 mmol/L), and the lowest activity was found in extracts from Ivusku Lake (0.31 ± 0.01 mmol/L). Correspondingly, the concentrations of HA in Audzelu and Ivusku Lakes were recorded as 45.2 and 27.4 mg/g, respectively. High concentrations of HA promoted in vitro cell growth upon short-term exposure (up to 6 h). Conclusions: The results show that high TPC correlates with AO status and sapropel extracts with higher concentrations of HA exhibit greater AO activity and promote in vitro cell growth, suggesting a perspective use for short-term topical therapeutic skin applications. However, higher concentrations over longer durations showed cytotoxic effects, indicating the need for further investigation.

Depth-dependent variations of physicochemical properties of sedimentary dissolved organic matter and the influence on the elimination of typical pharmaceuticals

Sedimentary dissolved organic matter (DOM) could exert a significant influence on the transformation of trace organic contaminants. However, the variations of sedimentary DOM properties with depth and their impact on trace organic contaminants biodegradation remain unclear. In this study, the qualitative changes in DOM properties with depth were assessed using spectral techniques. Specifically, within the sediment range of 0-30 cm, humic acid and fulvic acid fractions exhibited higher degrees of humification and aromatization at 10-20 cm, while hydrophilic fractions showed higher degrees of humification and aromatization at 20-30 cm. Furthermore, electrochemical methods were employed to quantitatively assess the electron transfer capacity of sedimentary DOM at different depths, which displayed consistent variation trend with humification and aromatization degree. The high degree of humification and aromatization, along with strong electron-accepting capability of DOM, significantly enhanced the biodegradation rates of tetracycline and ritonavir. To gain deeper insights into the influence of molecular composition of DOM on its properties, two-dimensional gas chromatography-quadrupole mass spectrometry analysis revealed that quinones and phenolic hydroxyl compounds govern the redox reactivity of DOM. Simulated experiment of DOM-mediated biodegradation of typical pharmaceuticals confirmed the role of quinones and phenolic hydroxyl groups in the redox reactivity of DOM.

Subcomponents in humic acid structure contribute to the differential responses of Aspergillus oryzae strains to humic acid

Humic acid (HA) is a complex natural organic macromolecule, can be decomposed to low-molecular compounds by some soil fungi and then influences the growth of fungi. Aspergillus oryzae is a fungus domesticated from its ancestor, which was supposed to live in soil. Group 3 strains of A. oryzae hold fewer aflatoxin-biosynthetic genes than group 1 strains and may differently response to HA because of the deletion of some genes along with the domestication. However, effect of HA on growth of A. oryzae group 1 and group 3 strains remains unclear. In this study, four strains of A. oryzae in group 1 and four in group 3 were point inoculated on equivalent medium (pH 7.3) with two commercially available HAs. The growth of RIB40 was the most stimulated among group 1 strains and that of RIB143 was the most inhibited among group 3 strains. To identify the basis of these differences, we examined the possible effects of HA subcomponents including polyphenol and minerals on the growth of RIB40 and RIB143. Polyphenol represented by gallic acid (GA), a partial structure common with model HA, and mineral ions including Al 3+ , Ca 2+ , Ti 4+ , Mn 2+ , Sr 2+ , and Ba2+ contributed to stimulating the growth of RIB40, whereas these components generally did not affect the growth of RIB143. Thus, our findings indicate that the sub-compositions of HAs, including GA and several minerals, were the main factors driving the different responses of RIB40 and RIB143 to HAs.

Different crystalline manganese dioxide and biochar co-conditioning aerobic composting: Reduced ammonia volatilization and improved organic fertilizer quality

Aerobic composting is a sustainable and effective waste disposal method. However, it can generate massive amounts of ammonia (NH3) via volatilization. Effectively reducing NH3 volatilization is vital for advancing aerobic composting and protecting the ecological environment. Herein, two crystal types of MnO2 (α-MnO2 and δ-MnO2) are combined with biochar (hydrochar (WHC) and pyrochar (WPC), respectively) and used as conditioners for the aerobic composting of chicken manure. Results reveal that α-MnO2 (34.6%) can more effectively reduce NH3 accumulation than δ-MnO2 (27.1%). Moreover, the combination of WHC and MnO2 better reduces NH3 volatilization (48.5-58.9%) than the combination of WPC and MnO2 (15.8-40.1%). The highest NH3 volatilization reduction effect (58.9%) is achieved using the combination of WHC and δ-MnO2. Because the added WHC and δ-MnO2 promote the humification of the compost, the humic acid to fulvic acid ratio (HA/FA ratio) dramatically increases. The combination of WHC and δ-MnO2 doubled the HA/FA ratio and resulted in a net economic benefit of 130.0 RMB/t. Therefore, WHC and δ-MnO2 co-conditioning can promote compost decomposition, improving the quality of organic fertilizers and substantially reducing NH3 volatilization.

PbO2 reductive dissolution by dissolved Mn(III) in the presence of low molecular weight organic acids and humic acid

Although Mn(III) complexes with organic ligands have been previously identified, the information about their stability and reactivity is scarce. In the present study, we analyzed the formation and stability of three different complexes: Mn(III)-citrate, Mn(III)-tartrate, and Mn(III)-humic acid (HA), as well as their reactivity toward an element of high environmental concern, lead (Pb).Our results indicate that the stability of studied complexes is highly dependent on pH. The Mn(III) complexes with citrate and tartrate degrade below pH 8, due to the electron transfer reaction between Mn(III) and the ligand, while the Mn(III)-HA complex's degradation is slower and less sensitive to pH. At pH 4, less than 40% of the initial Mn(III)-HA was found to be stable.The reactivity of the complexes was different depending on the ligand and its concentration. The Mn(III)-citrate and Mn(III)-tartrate complexes effectively reduced PbO2 and releases aqueous Pb2+, although significant differences were found with increasing ligand concentration. There was no evidence of the reduction of PbO2 by Mn(III) when it forms a complex with HA. This is likely due to the large size of HA moieties that prevent the Mn(III) component of the complex from getting close enough to the PbO2 surface to initiate electron transfer and lead to the reduction of Pb(IV) by HA itself.

Sustainable papaya plant waste and green tea residue composite films integrated with starch and gelatin for active food packaging applications

This study explores the sustainable utilization of wastes from a papaya plant (papaya peels (PP), papaya seeds (PS), leaf-stem (PL)) and dried green tea residues (GTR) for the synthesis of bioplastics. The dried GTR were individually blended with each papaya waste extract and then boiled in water to get three composite papaya plant waste-green tea supernatants. Potato starch and gelatin-based functional films were prepared by integrating each with the composite papaya waste-green tea supernatant liquid. This work introduces a dissolved organic matter (DOM) study to the field of bioplastics, with the goal of identifying the organic components and macromolecules inherent in the PW supernatants. When compared with the films prepared solely from papaya waste (PW) supernatants, PW-GTR composite supernatant films prevent UV light transmission with superior antioxidant and mechanical properties. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and atomic force microscopy (AFM) were utilized to characterize the starch and gelatin PW-GTR films. Owing to the exceptional antioxidant, UV barrier, and remarkable biodegradable properties of the starch/PW/GTR and gelatin/PW/GTR composite films, make them ideal for use in food packaging applications.

Degradation of Tetrabromobisphenol S by thermo-activated Persulphate Oxidation: reaction Kinetics, transformation Mechanisms, and brominated By-products

Brominated flame retardants (BFRs) are a group of contaminants of emerging environmental concern. In this study, systematic exploration was carried out to investigate the degradation of tetrabromobisphenol S (TBBPS), a typical emerging BFRs, by thermally activated persulfate (PDS) oxidation. The removal of 5.0 μM TBBPS was 100% after 60 min oxidation treatment under 60°C. Increasing the temperature or initial PDS concentration facilitated the degradation efficiency of TBBPS. The quenching test indicated that TBBPS degradation occurred via the attack of both sulphate radicals and hydroxyl radicals. Natural organic matter (NOM) decreased the removal rate, however, complete disappearance of TBBPS could still be obtained. Six intermediate products were formed during reactions between TBBPS and radicals. Transformation pathways including debromination, β-Scission, and cross-coupling were proposed. Brominated disinfection by-products (DBPs) in situ formed during the degradation of TBBPS were also investigated, such as bromoform and dibromoacetic acid. The presence of NOM reduced the formation rates of brominated DBPs. Results reveal that although thermo-activated PDS is a promising method for TBBPS-contaminated water, it can lead to potential brominated DBPs risks, which should be paid more attention to when SO4•--based oxidation technology is applied.

Porous polymer monolithic columns to investigate the interaction of humic substances with herbicides and emerging pollutants by affinity chromatography

BACKGROUND

Understanding the interaction mechanisms and the relevant binding constants between humic acids and emerging or regulated pollutants is of utmost importance in predicting their geochemical mobility, bioavailability, and degradation. Fluorescence spectroscopy, UV-vis spectroscopy, equilibrium dialysis, and solid-phase extraction combined with liquid chromatography-mass spectrometry have been employed to elucidate interactions of humic acids with organic micropollutants, especially pharmaceutical drugs. These methods demand large sample volumes, long equilibration times, and laborious extraction steps which may imply analytical errors. Monolithic high-performance affinity chromatography is an alternative and simpler method to investigate these interactions and determine the binding constants.

RESULTS

Polymer monoliths based on aminated glycidyl methacrylate and ethylene glycol dimethacrylate served to immobilize Cu(II) and then humic acid to produce monolithic affinity chromatography columns with humic acid as the active interaction phase. About 86.5 mg of humic acid was immobilized per gram of polymer. The columns enabled a comparison of the binding strength of humic acid with herbicides and emerging pollutants at 25 °C and pH 6.0 ± 0.1. Paracetamol, acetylsalicylic acid, and salicylic acid did not retain. Among the compounds that interacted with humic acid, the order of increasing affinity, estimated by the global affinity constant (nKa) or partition coefficient (KD) was: caffeine < simazine < atrazine ∼ propazine < benzophenone. The nKa (L mol-1) values ranged from (4.9 ± 0.3) × 102 for caffeine to (1.9 ± 0.3) × 103 for benzophenone, whereas KD (L kg-1) varied from 14 ± 1 to 56 ± 8 for the same compounds.

SIGNIFICANCE AND NOVELTY

To our knowledge, this is the first paper demonstrating the use of a monolithic platform to immobilize supramolecular structures of humic acids exploiting immobilized metal affinity to comparatively evaluate their affinity towards emerging pollutants exploiting the concepts of high-performance affinity chromatography. The proposed approach needs only small amounts of humic acid, which is a relevant feature in preparing columns with humic substances isolated and purified from remote areas.

Antioxidant Agriculture for Stress-Resilient Crop Production: Field Practice

Oxidative stress, resulting from the excessive production of reactive oxygen species, is a common and major cause of cellular damage in plants exposed to various abiotic stresses. To address this challenge, we introduce the concept of antioxidant agriculture as a comprehensive strategy to improve stress tolerance and thus crop productivity by minimizing oxidative stress levels in the field environment. This strategy encompasses a diverse range of approaches, including genetic engineering, the exogenous application of antioxidant agents, microbial inoculation, and agronomic practices, to reinforce the plant's intrinsic antioxidant defense system and mitigate oxidative stress. We present recent successful studies of antioxidant measures that have been validated in field conditions, along with our perspective on achieving antioxidant agriculture.

A change in substance and microbial community structure during the co-composting of kitchen waste anaerobic digestion effluent, sewage sludge and Chinese medicine residue

Anaerobic digestion is a resource recovery method for organic waste, gaining attention due to carbon reduction. Disposing of anaerobic digestion effluent (ADE) is crucial for developing anaerobic digestion, but conventional wastewater treatment fails to effectively recover nutrients contained in the ADE. In the present study, the ADE without solid-liquid separation was mixed with sewage sludge and Chinese medicine residue for the composting, where the ADE could be recovered at high temperature through humification. Besides, the nitrogen balance, humification process, and microbial dynamics during the composting process were studied. The results showed that the group supplemented with ADE could increase the nitrogen retention efficiency by 2.21 % compared to the control group. High ammonia nitrogen content and salinity did not negatively affect the maturity and phytotoxicity of compost products and even increase the humification degree of compost products. Moreover, additional ADE may not alter microbial community structure, which could contribute to microbial succession. This is the first time to investigate the substance transformation and shift in microbial community structure while applying composting process for ADE treatment, in which the anaerobic-aerobic collaborative disposal process provides an alternative solution for the recovery of ADE.

Solid-Phase Extraction at High pH as a Promising Tool for Targeted Isolation of Biologically Active Fractions of Humic Acids

A search for novel sources of biologically active compounds is at the top of the agenda for biomedical technologies. Natural humic substances (HSs) contain a large variety of different chemotypes, such as condensed tannins, hydrolyzable tannins, terpenoids, lignins, etc. The goal of this work was to develop an efficient separation technique based on solid-phase extraction (SPE) for the isolation of narrow fractions of HS with higher biological activity compared to the initial material. We used lignite humic acid as the parent humic material, which showed moderate inhibition activity toward beta-lactamase TEM 1 and antioxidant activity. We applied two different SPE techniques: the first one was based on a gradient elution with water/methanol mixtures of the humic material sorbed at pH 2, and the second one implied separation by a difference in the pKa value by the use of sequential sorption of HS at pH from 8 to 3. SPE cartridges Bond Elute PPL (Agilent) were used in the fractionation experiments. The first and second techniques yielded 9 and 7 fractions, respectively. All fractions were characterized using high-resolution mass spectrometry and biological assays, including the determination of beta-lactamase (TEM 1) inhibition activity and antioxidant activity. The acidity-based separation technique demonstrated substantial advantages: it enabled the isolation of components, outcompeting the initial material at the first step of separation (sorption at pH 8). It showed moderate orthogonality in separation with regard to the polarity-based technique. Good perspectives are shown for developing a 2D separation scheme using a combination of polarity and acidity-based approaches to reduce structural heterogeneity of the narrow fractions of HS.

Humic substance/metal-oxide multifunctional nanoparticles as advanced antibacterial-antimycotic agents and photocatalysts for the degradation of PLA microplastics under UVA/solar radiation

As a result of the accumulation of plastic in the environment, microplastics have become part of the food chain, boosting the resistance of fungi and bacteria which can frequently encounter human beings. Employing photocatalytic degradation is a possible route towards the removal of chemical and biological pollutants, such as plastics and microplastic wastes as well as microorganisms. Using biowaste materials to design hybrid nanoparticles with enhanced photocatalytic and antimicrobial features would uphold the principles of the circular bioeconomy. Here, two unexpensive semiconductors-namely titanium dioxide (TiO2) and zinc oxide (ZnO) - were synthetized through solvothermal synthesis and combined with humic substances deriving from agrifood biomass. The preparation led to hybrid nanoparticles exhibiting enhanced ROS-generating properties for simultaneous applications as antimicrobial agents against different bacterial and fungal strains and as photoactive catalysts to degrade polylactic acid (PLA) microplastics under UVA and solar irradiation. In comparison to bare nanoparticles, hybrid nanoparticles demonstrated higher antibacterial and antimycotic capabilities toward various pathogenic microorganisms as well as advanced photocatalytic activity in the degradation of PLA with a carbonyl index reduction in the range of 15-23%, thus confirming a noteworthy ability in microplastics photodegradation under UVA and solar irradiation.

New insights into the sustainable use of soluble straw humic substances for the remediation of multiple heavy metals in contaminated soil

This study addresses the research gap in understanding the differences in straw decomposition and variations in humic substances (HS) extracted from various treatment conditions. The aim is to explore the potential of soluble straw HS in remediating heavy metal pollution in soils. The study characterizes straw decomposition structures using scanning electron microscopy (SEM) and X-ray diffraction (XRD), while employing gel permeation chromatography (GPC) and fluorescence spectroscopy (EEM) to analyze the molecular weight and degree of humification of extracted straw HS. The removal efficiency of HS for heavy metals is assessed, with a focus on aerobic humic substances (AE-HS) showing the highest potential for heavy metal removal. Spectral analysis and mass spectrometry analysis reveal the role of phenolic compounds, carboxylic acids, and aromatic compounds in AE-HS, forming humates or complexes to remove heavy metals from contaminated soil. Notably, the optimized AE-HS achieved the highest removal efficiency of 96.18 %, 82.75 %, 60.43 %, and 41.66 % for cadmium, copper, zinc, and lead, respectively. This study provides new insights into the preparation of straw for use as a heavy metal remover and has implications for the use of straw humic substances in soil remediation.

New approach to soil management focusing on soil health and air quality: one earth one life (critical review)

Soil plays a key role in ecosphere and air quality regulation. Obsolete environmental technologies lead to soil quality loss, air, water, and land systems pollution. Pedosphere and plants are intertwined with the air quality. Ionized O2 is capable to intensify atmosphere turbulence, providing particulate matter (PM2.5) coalescence and dry deposition. Addressing environmental quality, a Biogeosystem Technique (BGT*) heuristic transcendental (nonstandard and not direct imitation of nature) methodology has been developed. A BGT* main focus is an enrichment of Earth's biogeochemical cycles through land use and air cleaning. An intra-soil processing, which provides the soil multilevel architecture, is one of the BGT* ingredients. A next BGT* implementation is intra-soil pulse continuously discrete watering for optimal soil water regime and freshwater saving up to 10-20 times. The BGT* comprises intra-soil dispersed environmentally safe recycling of the PM sediments, heavy metals (HMs) and other pollutants, controlling biofilm-mediated microbial community interactions in the soil. This provides abundant biogeochemical cycle formation and better functioning of the humic substances, biological preparation, and microbial biofilms as a soil-biological starter, ensuring priority plants and trees nutrition, growth and resistance to phytopathogens. A higher underground and aboveground soil biological product increases a reversible C biological sequestration from the atmosphere. An additional light O2 ions photosynthetic production ensures a PM2.5 and PM0.1 coalescence and strengthens an intra-soil transformation of PM sediments into nutrients and improves atmosphere quality. The BGT* provides PM and HMs intra-soil passivation, increases soil biological productivity, stabilizes a climate system of the earth and promotes a green circular economy.

Humic acids on fire? Physico-chemical, thermal, flammability features and extraction process of different humic acids in support of their possible applications

Humic acids (HA) consist in a multitude of heterogeneous organic molecules surviving the biological and chemical degradation of both vegetal and animal biomasses. The great abundance and chemical richness of these residues make their valorisation one of the most promising approaches to move towards a circular economy. However, the heterogeneity of the biomass from which HA are extracted, as well as the production process, significantly affects the nature and the relative content of functional groups (i.e. quinones, phenols and carboxylic and hydroxyl moieties), eventually changing HA reactivity and ultimately determining their application field. Indeed, depending on their properties, these substances can be used as flame retardants in the case of pronounced resilience degree (i.e., absent or low reactivity), or as antioxidant or antimicrobial agents in the case of pronounced reactivity, thanks to their redox behaviour. In this work we investigated the flammable, the thermal and the physico-chemical features of HA extracted from different composted biomasses to identify the reactivity or the resiliency of these moieties. Several techniques, including flammability characterization (LIT and MIE), laser diffraction granulometry, TG, XRD analyses, FTIR spectroscopy on both solid and gaseous phases, and Raman spectroscopy were integrated to investigate the correlation among the safety parameters, the distributions of particle sizes, as well as the thermal, the chemical properties of HA powders and the influence of post-extraction processes on HA final properties.

Preparation, characterization, bacteriostatic efficacy, and mechanism of zinc/selenium-loaded sodium humate

In recent years, metal-based complexes including selenium (Se) and zinc (Zn)-containing compounds have been widely explored for their therapeutic properties due to their roles in biological processes and modulation of diverse molecular targets. Humic acid, as a metal complexing agent, is also widely used in biomedical field. In this work, three kinds of modified sodium humate (HNa), including Zn-HNA, Se-HNa, and Zn/Se-HNa, were prepared by ion exchange reaction method. The modified HNa was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and elemental mapping. The bacteriostatic activity and mechanism of modified HNa against gram-positive and gram-negative bacteria were investigated by testing bacterial inhibition zone, minimum inhibitory concentration, and capacity to destroy integrity of the bacterial membrane, promoting ROS generation level and prevention of biofilms. FTIR results showed that HNa could combine with zinc ions and selenite ions. The main XRD peaks did not change significantly. In the modified HNa, the particle shape was irregular. Compared to HNa, Zn-HNA, and Se-HNa, Zn/Se-HNa showed the strongest bacteriostatic activity. Zn/Se-HNa exhibited high bacteriostatic activity against gram-negative bacteria (Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae) and gram-positive bacteria (Staphylococcus aureus), but showed weak antibacterial activity against another gram-positive bacteria, Bacillus subtilis. The bacteriostasis was achieved by altering the permeability of bacterial cell membranes, generating ROS, and preventing the formation of biofilms. In conclusion, Zn/Se-HNa has high bacteriostatic activity, making it a suitable alternative to antibiotics in fields like the treatment of trauma infections and animal husbandry. KEY POINTS: • Preparate and characterize zinc- and selenium-loaded sodium humate (Zn/Se-HNa). • The combination of Zn and Se enhanced the bacteriostatic activity of HNa. • Zn/Se-HNa alters the permeability of bacterial cell membranes and promotes generation of ROS.

Efficient recovery and characterization of humic acids from municipal and manure composts: A comparative study

The recovery of humic acids from low-quality compost obtained in municipal solid waste treatment plants provides opportunities for its valorization. This study compares the recovery and properties of the humic acids obtained from municipal mixed waste compost (MMWC) and manure compost. The effects of temperature, time, and KOH concentration on the ratio of humic acids in the extracted liquid and the content of organic carbon of the precipitates were investigated by response surface methodology. Optimal conditions were 30 °C and 24 h for both composts, with a KOH concentration of 0.53 M for MMWC and 0.25 M for manure compost. The manure compost provided a liquid extract richer in humic acids than MMWC (76.6 % vs. 33.7 %), but the precipitates presented similar organic carbon contents (38.1 % vs. 42.4 %). Regarding composition, both humic acids presented higher organic carbon and nitrogen contents than the composts used as feedstock. The extraction and further precipitation of humic acids reduced the concentration of heavy metals. Humic acids from manure compost have a slightly higher average molecular weight (2650 Da) than those from MMWC (1980 Da), while both present similar C/N ratios and degree of aromaticity. Most contaminants of emerging concern present in the original composts were not detected in the humic acids. Thus, it was demonstrated that MMWC constitutes an attractive source of humic acids with properties similar to those obtained from a high-quality compost and, therefore, with potential economic value.

Physically and Chemically Cross-Linked Poly(vinyl alcohol)/Humic Acid Hydrogels for Agricultural Applications

The preparation method of hydrogels has a significant effect on their structural and physicochemical properties. In this report, physically and chemically cross-linked poly(vinyl alcohol) (PVA) networks containing humic acid (HA) were alternatively prepared by autoclaving (AC) and through glutaraldehyde (GA) addition, respectively, for agricultural purposes. PVA/HA hydrogels were comparatively characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, mechanical assays, scanning electron microscopy, swelling kinetics measurements, and water retention tests in soil. AC hydrogels showed a more homogeneous porous microstructure, higher swelling levels, and a better capacity to preserve the humidity of soil than those obtained by adding GA. Both PVA/HA hydrogels exhibited no phytotoxicity on cultivation trials of Sorghum sp., but the plant growth was promoted with the GA-cross-linked network as compared to the effect of the AC sample. The release behavior of urea was modified according to the preparation method of the PVA/HA hydrogels. After 3 days of sustained urea release, 91% of the fertilizer was delivered from the AC hydrogel, whereas a lower amount of 56% was released for the GA-cross-linked hydrogel. Beyond the advantages of applying PVA/HA hydrogels in the agricultural field, an appropriate method of preparing these materials endows them with specific properties according to the requirements of the target crop.

Production of artificial humic acid from corn straw acid hydrolysis residue with biogas slurry impregnation for fertilizer application

This study investigated hydrothermal humification of corn straw acid hydrolysis residue with biogas slurry impregnation, aiming at producing water-soluble artificial humic acid fertilizer for fertilizer application and soil remediation. Hydrothermal humification parameters, including potassium hydroxide concentration (1-3 mol/L), retention time (2-6 h), and temperature (140-180 °C), were investigated using water as the liquid phase. The selected hydrothermal humification condition was 1.5 mol/L potassium hydroxide at 180 °C for 4 h. Moreover, biogas slurry impregnation (0-30 days) was evaluated to improve humic acid yield without introducing additional chemicals or energy input. Biogas slurry as the liquid phase increased the humic acid production by 73.24% with 5 days of impregnation compared to the control due to the alkalinity. The humic acid concentration was sufficient for China's national standard of water-soluble humic acid fertilizers in such conditions. The organic components in biogas slurry were involved in artificial humification as a precursor, forming C-N bonds with humic acid. The product with fortified nitrogen-containing functional groups enhanced the nutrient slow-release characteristics and water retention capabilities. The pot experiment further confirmed that artificial humic acid prepared in this study not only promoted the growth of plants but also achieved soil remediation.

Nano-Biochar Enhances Wheat Crop Productivity by Vindicating the Effects of Drought: In Relation to Physiological and Phenological Stages

Climatic changes are major hindrances to crop productivity. Likewise, water scarcity is the major obstacle during different physiological and phenological stages, which ultimately reduces the wheat crop yield. So, there is a dire need to adopt modern approaches such as soil amendments, i.e., using nano-biochar (NBC) to boost soil health and wheat crop productivity. Therefore, a case study was performed in the wire house of the Agronomy Department, Faculty of Agriculture and Environmental Sciences, Islamia University of Bahawalpur. CRD (completely randomized design) with four treatments of NBC, i.e., NBC0 (control), NBC1 (0.5%), NBC2 (1.00%), NBC3 (1.5%), and four drought levels D0 = control, D1 = drought at tillering, D2 = drought at flowering, and D3 = drought at grain filling was used. The hypothesis for the case study was to investigate if the NBC increases crop productivity by boosting physiological and chemical attributes under different drought conditions at different phenological stages. Results showed that among NBC treatments, NBC2 (1.00%) showed 37.10% increase in peroxidase activity, 28.60% in superoxide dismutase, 63.33% in catalase, 22.03% in ascorbate peroxidase, and 6.66% in plant height as compared to other NBC treatments, whereas among drought treatments, D0 = control stood out in comparison to water deficit treatments at critical growth and development stages, statistically analyzed data revealed that D0 was able to generate plant height 6.17 times more, 12.76% in the number of grains per spike, 4.60% in osmotic potential, and 2.96% in stomatal conductance activities of wheat crop. D3 and NBC0 were identified as treatment levels with the statistically lowest growth and yield returns, respectively. It showed a decrease of 4.69% in leaf relative water contents, 12.33% in water potential, and 23.64% in fertile tillers. It was recommended that drought is avoided at any critical growth, particularly at the grain-filling stage. The use of organic substances (fertilizers) must be promoted as they possess soil and crop health-promoting properties and also reduce different management expenses (fertilizer cost). Using NBC helps boost crop growth in the presence of a limited water supply. However, extensive research is needed to find out the impact of these organic substances (humic acid, farmyard manure, and NBC) on different crops, particularly on wheat, under stress conditions.